Coated abrasives



6, 1966 w. F. TIMMER ETAL 3,265,873

COATED ABRASI VES Filed June 23, 1962 E W M W N 00% O H 2A. S T M w w IIO m m P E G: w mm 5 .WW UL R B G O 0 w 4 2 DILUENT HARDNESS (MOH SCALE) INVENTORS WILLIAM F. TIMMER NOLAN A. CURRY BY M9/m' ATTORNEY United States Patent 3,266,878 COATED ABRASIVES William F. Timmer, Cohoes, and Nolan A. Curry, Troy,

N.Y., assignors to Norton Company, Troy, N.Y., a corporation of Massachusetts Filed July 23, 1962, Ser. No. 211,770 7 Claims. (Cl. 51-298) The present invention relates in general to coated abrasives and more particularly to an improved coated abrasive product.

Heretofore, the usual abrasive grains used in the manufacture of coated abrasives have been the naturally occurring flint, garnet and emery and the electro-furnace grains such as aluminum oxide and silicon carbide. For special purposesusually the polishing of extremely hard surfaces such as tungsten carbide diessparing use has been made of diamonds as the abrasive media. In this area of usage most of the emphasis has been on the makeup of the backing for the abrasive since diamonds constitute an expensive grit and efforts have correspondingly been made to produce long-wearing backings such as leather (US. 2,410,506) and nylon (US. 2,712,987).

Where diamonds have been employed, it has commonly been accepted as basic abrasive fact that a surface of 100% diamonds would out-cut a surface carrying a lesser percentage of'diamond grit and the only use for any diluent abrasive with diamond grit has been to provide more uniform distribution of the diamonds over the belt and to provide a control for decreasing the cut of the belt or other diamond abrasive article by increase in the percentage of diluent. fact, US. 2,410,506 illustrates abrasive surfaces wherein the diamond grit is cut or diluted with varying percentages of another abrasivesilicon carbide. According to prior art theory, the use of silicon carbide as shown in US. 2,410,506 was indicated since this readily available and relatively inexpensive abrasive grain approaches diamond in hardness-having a Moh hardness of 9.5 as compared to diamonds 10.

However, it has now been found that, most surprisingly, the cut of a diamond abrasive surface can actually be increased by diluting the diamond abrasive with a different material in discrete particle form having a Moh hardness within the range of 4.0 to 8.5.

Accordingly, it is an object of the present invention to provide an improved coated abrasive product utilizing diamonds as at least a portion of the abrading media there- Another object of the invention is to provide an improved diamond-surfaced coated abrasive having improved cut over a similar product utilizing 100% diamond abrasive.

A further object of the invention is to provide a diamond-surfaced coated abrasive product having improved cutting properties at a lower production cost.

Additional objects, if not specifically set forth herein, will be readily apparent to one skilled in the art from the following detailed description of the invention.

In the drawings:

FIGURE 1 is a graph illustrating the improvement in cutting ability, in terms of grams of tungsten carbide, resulting from the change in hardness of a diluent abrasive blended with a diamond abrasive, the volume of the different diluent abrasives being held constant.

In accordance with this accepted "ice Generally, the present invention comprises the provision of a coated abrasive product wherein the abrading grain used is a blend of diamond grit and a diluent having a Moh hardness of from 4.0 to 8.5.

More specifically, the present invention contemplates substituting, in a construction such as is illustrated in US. 2,712,987, for the 100% diamond abrasive a diluted diamond abrasive containing from 25 to by volume of a grain having a hardness on the Moh scale ranging from 4.0 to 8.5.

As illustrated in FIGURE 1, it has been found that although dilution of diamond grit with a hard abrasive diluent such as silicon carbide (Moh 9.5) causes a sharp decrease in the cutting ability of products made therefrom, as the hardness of the diluent is still further decreased the cut begins to climb, equalling that of 100% diamond at about a Moh hardness of 8.5 and then going on to exceed the cut of 100% diamond. Still further reduction in hardness of the diluent produces a gradual decline in cut after a Moh hardness of about 7.5 until at a Moh hardness of about 4.0 the cut has dropped substantially below 100% diamonds, although still above that obtained when the diluent is silicon carbide having a Moh hardness of 9.5.

In the practice of the present invention, it is considered that any conventional backing or bond may be used for the abrasive grain and there is no intention of limiting the invention to any particular type of backing or bond.

Suitable backings may be formed from paper, cloth, fiber, leather, nylon or other plastic and the like. However, it is preferred to use a cotton fabric, either plain or twill weave, saturated with a Waterproofing material. The preferred cloth construction for narrow belt usage is a 38 X 30, 1 x 1 plain weave fabric having a weight of 23.2 pounds per ream. The saturant is any of the standard Waterproofing saturants heretofore used in the manufacture of waterproof coated abrasives, e.g. polyvinyl butyral or ethyl cellulose-phenolic resin blend, etc., and usually is applied in from 25 to 40% by weight based on the cloth backing.

As a binder to secure the abrasive grain blend to the backing, it is preferred to use a phenol-formaldehyde resin adhesive although other adhesives such as epoxy resins, ure-aformaldehyde resins and the like may be used.

The diluent material may be any material capable of being formed into discrete particles and having a hardness within the range of 4 to 8.5 on the Moh hardness scale. In addition to the commonly used abrasive materials such as fiint, garnet and emery, the diluent materials found usable in the present invention have ranged from ground phenolic resin particles (filled or unfilled) to ground glass. The particle size of the diluent is not critical in that it can be varied to some extent without causing any serious variation in the results achieved. Generally the particles should be of approximately the same screen size as the diamond abrasive although the shape of such particles may vary from a needle shape to a cubical shape or spherical shape. By screen size is meant the size of particle which will pass a screen having a given number of openings per square inch. Generally these materials have been referred to herein and in the appended claims r as diluent grains in order to indicate that in all instances discrete particles are present.

The following specific examples are illustrative only of products made in accordance with the present invention and no limitation is intended other than as may appear in the appended claims.

Example I The abrasive blends used in the present invention are very simply made by rolling a mixture of grains containing the desired percentage of diamond grit and diluent grain until a fairly uniform mixture is obtained. A typical blend was made by Weighing out .350 ounce of 100 mesh grade natural industrial diamond (synthetic diamond may be substituted if desired) and .650 ounce of an equivalent grade (fine or 2/0) flint. This mixture was rolled in a tumbling mixer for a period of minutes to obtain a uniform blend of the abrasive grain.

Example 2 An abrasive belt was formed using as a backing arm endless cotton belt. The fabric used in the backing was a plain weave cotton having a 38 x 30, 1 x 1 construction and weighing approximately 23.2 pounds per ream. The belt was then saturated with a blend of vinyl acetate-vinyl chloride copolymer as described in Example 1 of US. 2,357,350. The total pick-up of saturant was about 34%. After saturation, the fabric was dried at 160 F. for one-half hour whereupon a backsize of a slurry of pelletized graphite and phenolic resin in denatured alcohol (55 parts phenolic to 45 parts graphite to 15 parts alcohol) was then applied by a doctor knife to the saturated cloth in an amount of approximately 40% by weight of the original cloth weight. The backsize was then dried and cured for about 1 hour at 250 F.

The material treated as above was in the form of an endless belt, 4" wide x 75 long. It was next slit to the desired widthin this case, x 75". The maker adhesive consisting of a phenolic resin adhesive was then applied to the surface of the belt and a blend of 35 parts diamonds and 65 parts fiint (both 100 mesh) abrasive was applied uniformly to the adhesive. The total weight of grain was 0.63 gram. This product was then heated at 200 F. for about 1 hour and at 255 F. for 30 minutes to cure the maker adhesive whereupon a size adhesive of a phenolformaldehyde resin was appplied over the abrasive and cured for about two hours at about 225 F. and at one hour for 300 F. The finished belt was found to be capable both of polishing tungsten carbide and also of removing stock in a cutting operation.

Example 3 On -a backing similar to that of Example 2 except that as the waterproofing saturant a rubber saturant of the type disclosed in US. 2,236,597 was substituted for the vinyl acetate-chloride saturant of Example '2, was coated a phenolic resin-abrasive slurry coat. This slurry consisted of 50 parts by weight of 4052 micron diamond grit blended with parts by weight of equal size flint particles. Total abrasive weight applied was 0.05 grams/ in. of backing. The cure applied was equivalent to both the size and maker cure given in Example 1. No added size was applied in this case. Discs cut from this material were found to both polish tungsten carbide and to also effect stock removal.

Example 4 Using the abrasive belt of Example 1 and varying the diluent content of the diamond as to type but holding the percent by volume of diamond constant at 29.8%, a series of such abrasive belts were made up and run against a type 883 tungsten carbide rod of initial /2" diameter. The belt speed and tension was identical in each case and the carbide rod was rotated against the belt'at l930revolutions per minute. The grit size was 100 mesh in each instance. A water spray was applied to the point of contact between the belt and the carbide rod. After 200 minutes running the amount of carbide removed was measured by weighing the rod with the following results:

Diluent Tungsten Abrasive Moh Carbide Hardness Grams Removed All Diamond 10 28. 54 SiO.-Diamond 9. 5 22. 99 Al O Diam0nd 9. 0 26. 73 E1neryDiamond 8. 0 36. 74 GarnetDiamond 7-7. 5 32. 14 FlintDiamond 6. 0 29. 20

Example 5 Diluent; Tungsten Abrasive Moh Carbide Hardness Grams Removed Ground Resin-Diamond 5-6 36. 06 RosinO ACO -Dia1n0nd 5-6 37. 87 Ground GlassDiamond 5-6 37. 00

By comparison, a blend of the same volume of diamond but using a diluent (Magnorite) having a hardness slightly below 4, under the same conditions removed but 26.27 grams of tungsten carbide.

In general, any of the available sizes of diamond abrasives may be used in the present invention, with the diluent grain being, in each instance, of approximately the same particle size as the diamond used. Where reference is made to parts by weight in the formation of some of the abrasive blends illustrated herein, it will be noted that correction has been made for specific gravity and in all instances the range of volume percent of diluent is between 25 and Likewise, the present invention is in no way limited to any particular type of backing, saturant or abrasive binder, these components being adequately and fully described in the prior art and generally capable of use with the present invention according to ordinary skill of one versed in the abrasive art.

Obviously, many variations and modifications may be made without departing from the spirit and scope of the invention disclosed herein and therefore only such limitations should be imposed as appear in the appended claims.

We claim:

1. In a coated abrasive product having a backing member and at least one coat of adhesive bonding an abrasive grain layer firmly thereto, the improvement which comprises:

(a) An abrasive grain layer containing a substantial proportion by volume of diamond grit,

(b) And the balance by volume consisting essentially of a diluent grain having a Moh hardness of from 4.0 to 8.5.

2. A coated abrasive product as in claim 1 wherein the percentage by volume of said diluent grain ranges from 25% to 85 3. A coated abrasive product as in claim 1 wherein the diluent grain is flint.

4. A coated abrasive product as in cIaim I wherein the diluent grain is emery.

References Cited by the Examiner UNITED STATES PATENTS 230,202 7/1880 Sibley 51 301 2,117,513 5/1938 Scuttetal 51 298 6 Coes a- 5l298 Brown 51298 Kirchner et a1 51298 X Williamson 51300 Zalud 51-298 Gregor 51-307 ALEXANDER H. BRODMERKEL, Primary Examiner.

MORRIS LIEBMAN, ALFRED L. LEAVITT,

Examiners.

D. J. ARNOLD, Assistant Examiner. 

1. IN A COATED ABRASIVE PRODUCT HAVING A BACKING MEMBER AND AT LAST ONE COAT OF ADDHESIVE BONDING AN ABRASIVE GRAIN LAYER FIRMLY THERETO, THE IMPROVEMENT WHICH COMPRISES: (A) AN ABRASIVE GRAIN LAYER CONTAINING A SUBSTANTIAL PROPORTION BY VOLUME OF DIAMOND GRIT, 